Hematologic Malignancies Program

Childhood Acute Lymphocytic Leukemia

What is Childhood Acute Lymphocytic Leukemia?

Childhood acute lymphocytic leukemia (also called acute lymphoblastic leukemia or ALL) is a disease in which too many underdeveloped lymphocytes (infection-fighting white blood cells) develop in a child's blood and bone marrow.

Lymphocytes are made by the bone marrow and by other organs of the lymph system. Bone marrow is the spongy tissue inside the large bones in the body. Bone marrow cells are produced by immature immortal stem cells.

These cells produce slightly more mature cells called blasts that develop (mature) into the following types of blood cells that have specific jobs to do in the body:

Red blood cells carry oxygen and other materials to all tissues of the body.
White blood cells fight infection.
Platelets make the blood clot.

Lymphocytes are found in the lymph, a colorless, watery fluid in the lymph vessels. The lymph vessels are part of the lymph system, which is made up of thin tubes that branch, like blood vessels, into all parts of the body.

Along this network of vessels are groups of small, bean-shaped organs called lymph nodes. Clusters of lymph nodes are found in the underarm, pelvis, neck, and abdomen. The spleen (an organ in the upper abdomen that makes lymphocytes and filters old blood cells from the blood), the thymus (a small organ beneath the breastbone), and the tonsils (an organ in the throat) are also part of the lymph system.

Lymphocytes fight infection by making antibodies, which attack germs and other harmful bacteria in the body. In childhood acute lymphocytic leukemia, the developing lymphocytes do not mature and they become too numerous.

The immature lymphocytes collect in the lymph tissues and make them swell and may crowd out other blood cells in the blood and bone marrow. Because of this crowding, if the bone marrow cannot make enough red blood cells to carry oxygen, then anemia may develop.

If the bone marrow cannot make enough platelets to make the blood clot normally, then bleeding or bruising may develop more easily. The cancerous lymphocytes can also invade other organs, the spinal cord, the brain, and the tonsils.

This page was last updated on: March 3, 2008.